Good questions, I also have the same thoughts. Let's see how dev will answer it.I hope we can get a solid and accurate answer from this. For now. lets help the project to increase popularity.
The answer is obvious, Saifu is full centralized and regulated and all you assets will be store in one account which means you won't have any private key ! they said our customers can leave the security worries to us. In other words, they will hold your private key, you don't need to deal with that. So if want to control you private key, Saifu is not for you.